Method of manufacturing cathode ray tubes, more particularly television picture tubes



Oct. 6, 1959 T c GROO'I' Em 2,907,619

THOD OF MANUFACTURING CATHODE RAY TUBES, MORE PARTICULARLY TELEVISION PICTURE TUBES Flled Sept. 30, 1957 3 Sheets-Sheet ILv oRDINARY METHOD INYENTIVE METHOD INvENTIoN +GLAZE JOINING com; 10 NECK JOINING OoNE TO NECK JOINING oNE TO NEtK covERINs FACE-RIM JoININc QONETO FACE JOINING ooNE 1'0 FACE WITH GLAZE l l CORNING N2 543 COOLING DowN TII.I. DD LING DowN TILL ROOM TE TuRE ROOM TEMPERATURE (ABOUT 1 4 HOUR) (ABOUT 174 mm) SEDIMENTATION OF sEDINIENTATIoN or SEDIMENTATION or FLuoREscENT LAYER FLUORESCENT LAYER FLUORESCENT LAYER DRYING LAYER AT DRYING LAYER AT DRYING LAYER AT ABOUT Iooc ADouT 1ooc AaouTIoo c PROVIDING oRsANIc PROVIDING ORGANIC PROVIDING NITROCEL- NITRocELLuLosE LAYER NITRocELLuLosE LAYER LULOSE LAYER DRYING 'oRcANIc LAYER DRYING ORGANIC LAYER DRYING ORGANgC LAYER ATIoo c I AT 100% AT 100 c PROVIDING METAL- PROVIDING M TAL- PROVIDING METAL- BACKING ON vAc. PUMP BACKING 0N vAc PuNIP BACKING IN vAc. ROOM HEATING TILL 375C IN ovEN AND auRNINc THE ORGANlC LAYER AND COOLING DowN (ABOUT 2 HouRs) (coNTINuED oN sNEET a) (coNTINuED 0N SHEET 2) (coNTINuED oN SHEET 2) INVENTORS Oct. 6, 1959 GROOT ETAL 2,907,619

T. C. METHOD OF MANUFACTURING CATHODE RAY TUBES. MORE PARTICULARLY TELEVISION PICTURE TUBES Flled Sept. 30, 1957 3 Sheets-Sheet 2 I SHEET.2

SEALING BOTTOM PIECE WITH ELECTRON GUN TO NECK PORTION.

SEALING BOTTOM mace WITH emcmoN suN TO NECK PORTION.

SEALING BOTTOM PIECETIITH ELECTRON GUN TO NECK PORTION.

TRANSPORTATION 1o STRAIGHT LINE OVEN MOUNTING EXHAUST TLBE'IO HIGH wmw PUTTING ON THE EXHAUST PUMP.

TRANSPORTATION TO STRAIGHT LINE OVEN AN) MM ING EXHAUST TUBE TO HIGH VICUW PUMP TRANSPORTATION FACE AND CGIE TO STRAIGHT LINE OVEN AND CONNEC- TING EXHAUST TUBE TO HIGH VACUUM m WHILE PLACING FACE ON THE CONE.

usxnua UP THE cm TILL 4ooc WHILE EVACUATINC THE sum. (out so MIN.)

(commune SHEET 3) HEATING UP TIU. 4soc,

AIR REMAINING IN auu,

mo aummo THE ORGANIC LAYIR. (our 40mm) HEATING UP TILL 475 c,

mus SEALING FACEI'O CONE av II-IE cLAzE,

ANo BURNING 11-IEORGANIC LAYER. IAaoIn 40mm) ACTIVAIING TH E A VACUUM PUMP! uwenmune AT 4ooc.

IAaouI 10mm.)

ACTIVATING THE VACUUM pumg. IAaouT Io MIN) (12w. ABOUT 4ooc) (CONTINUED SHEET 3) (CONTINUED SHEET 3) INVENTORS ROOT Oct. 6, 1959 T. C. GROOT ET AL METHOD OF MANUFACT PARTICULARLY TELEVISION PICTURE TUBES 3 Sheets-Sheet 3 Filed Sept. 30, 1957 SH EET.3

URING CATHODE RAY TUBES, MORE HEATING THE CATHODE FOR ACTIVATION HEATING THE CATHODE FOR ACTIVATION HEATING THE CATHODE FOR ACTIVATION SEALING THE EXHAUST TUBE AND COOLING DOWN TILL ROOM TEMP.

SEALING THE EXHAUST TUBE AND COOLING DOWN TILL ROOM TEMP SEALNG THE EXHAUST TUBE AND COOLING DOWN TILL ROOM TEMI? TAKING THE CRT OFE TAKING THE CRT OFE TAKING THE CRT OF FINISHING J FINISHING l V FINISHING United States Patent METHOD OF MANUFACTURING CATHODE RAY TUBES, MORE PARTICULARLY TELEVISION PICTURE TUBES Theodorus Cornelis Groot and Johannes Cornelis Jan- Application September 30, 1957, Serial No. 687,279

application Netherlands October '1, 1956 5 Claims. (Cl. 316-21) New York, N. a corporation Claims priority,

The invention relates to a method of manufacturing cathode ray tubes, more particularly television picture tubes, which are provided with a phosphor screen, to the cathode side of which is applied a thin metal layer or backing (aluminizing). r

Such tubes are manufactured as follows:

In a sealing machine the window or faceplate and the cone portions of the bulb are sealed to one another. The cone has already been provided with a neck portion. Then the bulb is annealed in a furnace and cooled down to room temperature in about 1% hours. The phosphor screen is then applied by settling and dried, which may be carried out for example, in a moderately heated furnace (about 100 C.). After cooling an organic intermediate (lacquer) layer consisting of a 2.5% solution of nitrocellulose in butylacetate is applied to the screen and dried at about 100 C. The neck is then connected to an auxiliary vacuum pump after a metal body has been introduced into the bulb in a manner such that the metal can be evaporated and precipitated on the organic inter mediate layer.

Then the intermediate layer is burnt out or combusted in a furnace in an oxygen-containing atmosphere, to this end the bulb is heated to 350 C. to 400 C. and again cooled to room temperature. This operation lasts about 2 hours.

The assembly is then introduced into a large straightline furnace after a bottom part or stem tube, which is provided with an exhaust tube and to which the electron gun is secured, has been sealed in the open end of the neck. The tube is then placed on an exhaust pump and assignors to North American.

ice

. 2 of the intermediate layer may be furthered by raising the temperature during the heating period till 45 0 C. instead of 400 C. Damage to the cathode and oxidizing of the metal part of the electron gun during the combustion of the intermediate layer are avoided by surrounding the neck with a heat. insulating screen, so that the electron gun andthe cathode remain comparatively cold. After the air has been evacuated from the tube, this heat-screen is remov'cchso that the operations to be carried out in the second half. of the furnace can take place inthe conventional manner. The invention provides the great advantage that the furnace for combusting the intermediate layer is completely omitted, as well as the heating and cooling in this furnace, which would take much time.

A further simplification and economy may be obtained in that the faceplate and the cone are not sealed directly to one another, but with the intermediary of a glaze. A

suitable glaze is known under the registered trade name Corning 543. Then first the fluorescent screen, the nitrocellulose intermediate layer and the metal backing may be applied to the faceplate and the edges of the screen *and/ or the cone may be painted with a suspension of the above mentioned glaze-powder in water, to which, if desired; a small quantity of Waterglass is added, the faceplate and cone being placed one on the other loosely but' centered, on the exhaust device, after the bottom part with the electron gun and the exhaust tube has been sealed in the opening of the neck, the glaze melting during the aforesaid heating and combustion of the intermediate layer or immediately thereafter, the faceplate being thus secured to the cone. To this end it is desirable when using the above-mentioned glaze, to raise locally the temperature of the furnace for example to 475, and to reduce the temperature to 420 at the exhaust area. The glaze which is still slightly soft, is then reduced to a very thin layer between faceplate and cone owing tothe pressure of the air on the faceplate. When using glaze or, if desired, an enamelled metal ring between faceplate and cone, the aforesaid sealing machine may also be omitted. However, in this case the metal coating must be applied in a vacuum furnace to the open, dish-like faceplates; which however does not involve any appreciable complication because a large number of faceplates may be treated simultaneously.

moved into the straight-line furnace, after the exhaust pump has been made operative.

In the straight-line furnace the tube is heated in about minutes to a temperature of 400 C., so that the bulb, the electrodes andthe screen are degasified. Beyond the centre of the furnace 'the cathode is heated and activated after which the exhaust tube is sealed off and the tube is slowly cooled down to room temperature. After a few external operations the tube is then ready.

In accordance with the invention it has been found that this method can be materially shortened and rendered much cheaper by burning the organic intermediate layer during the heating period in the straight-line furnace and by starting the exhaust of the tube not until the intermediate layer is burnt. The tube is then connected with its exhaust tube to the pump, it is true, but the pump 1s actuated not until the intermediate layer is burnt, i.e. near the centre of the furnace. It has been found that the reduction of the degasification period of the tube does not bring about disadvantages since most of the gas is set free when the tube reaches the highest temperature during the degasification period. The quantity of oxygen of the air contained in the tube is found to be sutficient for the intermediate layer to be burnt. The combustion his evident that with respect to the temperatures and the order of succession of the various treatments small variations are permitted Within the scope of the invention.

In order to point out the differences between the inventive method and the prior art, a flow chart has been shown in the accompanying drawing. In the flow chart are arranged alongside one another, reading from left to right, the succession of steps required to manufacture a cathode-ray tube in accordance with the prior art, in accordarge with the invention, and in accordance with the invention including the feature of the glaze for joining together the faceplate and cone. The identical steps in the three processes are arranged next to one another, so that the absence of a block indicates eliminatron of a step. For example, note that the precombustion step of the prior art, which consumed about two 7 hours of time, has been eliminated in the inventive processes.

thereafter evacuating the tube'while the heating is continued to outgas its elements, and thereafter activating {the ca hod 2 A method of manufacturing acathode-ray tube with. a metal-backed, pho phor screen, comprising the steps f, pr din an. o ganic intermediate ay r on e P phor screen. and a, metal-backing layer on the organic layer, thereafter assembling an, electron. gun in position. within the tube and sealing 01f the tube with. an air atmosphere, while. the organic layer remains, on the screen, thereafter; heating the tube with itsv air atmosphere and at a temperature at which the organiclayer is combusted and eliminated, immediately thereafteri evacuating the tube while the. heating is continued to outgas the electrodes of the electron gun and the other parts of the tube, and thereafter activating the cathode.

3- A me hod. of nufacturing a, cathode-ray tube with a metal-backed, phosphor screen, comprising the steps. of providing an organic intermediate. layer on. the phosphor screen and a metal-backing layer 011, the organic layer, thereafter sealing an, electron gun including a cathode in position within the tube while the organic layer remains on the screen and in such manner that. the tube contains an atmosphere, thereafter placing the tube. within a furnace and heating the tube at a. temperature. and for a time interval at which the organic layer is. combusted and eliminated, immediately thereafter evacuating the tube for a time interval shorter than. that of the previous 4 a step while the heating is continued and the tube remains at the high temperature of the previous step to outgas all of the tube elements, and thereafter activating the cathode.

4. A method as set forth in claim 3 wherein the temperature of the combustion is slightly higher than that of he ou aes n t p,

5. A method of manufacturing a cathode-ray tube with v a metal-backed, phosphor screen, comprising the steps of providing an organic intermediate layer on a phosphor screen on the faceplate of the tube and a metal-backing layer on the organic layer, assembling an electron gun into the cone; portion of the tube, applying to the edges of the faceplate and-the cone portion of the tube a glazing material, thereafter assembling the tube by juxtaposing the faceplate and cone portions so that the glazecovered edges abut while the organic layer remains, on the screen, thereafter heating the tube in an oxygen-contain: ing atm'opshere and at a temperatureat which the organic layer is combusted and, eliminated and the glazing material softened to seal together the faceplate and cone portions. of. the tube, immediately thereafter evacuating the tube. while the heating is continued tooutgas its elements, and thereafter activatingtthe cathode.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A METHOD OF MANUFACTURING A CATHODE-RAY TUBE WITH A METAL-BACKED, PHOSPHOR SCREEN, COMPRISING THE STEPS OF PROVIDING AN ORGANIC INTERMEDIATE LAYER ON THE PHOSPHOR SCREEN AND ON A METAL-BACKING LAYER ON THE ORGANIC LAYER, THEREAFTER ASSEMBLING THE TUBE WITH AN ELECTRON GUN IN POSITION THEREIN WHILE THE ORGANIC LAYER REMAINS ON THE SCREEN, THEREAFTER HEATING THE TUBE IN AN OXYGENCONTAINING ATMOSPHERE AND AT A TEMPERATURE AT WHICH THE ORGANIC LAYER IS COMBUSTED AND ELIMINATED, IMMEDIATELY THEREAFTER EVACUATING THE TUBE WHILE THE HEATING IS CONTINUED TO OUTGAS ITS ELEMENTS, AND THEREAFTER ACTIVATING THE CATHODE. 